The present invention relates to methods for controlled dewatering of confined, saturated formations in excavation mines.
In excavation mining, confined, saturated formations (e.g., sandstones and vugular formations) are lithologies saturated with water that are confined by a barrier lithology like smectite shale that is relatively water impermeable. The confined, saturated formations can hold significant volumes of water. Breach of the barrier of the confined, saturated formation, allow for the water of the confined, saturated formation to enter the mine and potentially flood the mine putting workers and equipment at risk. In some instances, when breached, the water within the confined, saturated formation can drain with significant force and quickly flood the mine, which is a significant risk to workers lives. Further, once a mine floods, pumping the water to the surface can take weeks, which is energy intensive and decreases mine productivity and profitability and makes difficult reaching workers that may be trapped in non-flooded areas.
To mitigate flooding, geologic data, like drilling and seismic data, may be used to provide general locations of the confined, saturated formation, which are then either avoided or underground rigs are used to drill through the barrier of the confined, saturated formation for draining. However, in some instances, draining via underground rigs cannot sufficiently keep up with the rate at which the water flows from the confined, saturated formation, which leads to flooding of the mine. Further, as the flooding is because of a high rate of water, the flooding is often fast and unexpected, which is a high risk to workers.
Therefore, a need exists for improved methods that can control the rate at which the water is released from the confined, saturated formations.